CHAPTER V. 



MAINTENANCE REQUIREMENTS OF AN ANIMAL AT 

 REST, AND WORKING REQUIREMENTS. 



Before deciding what amount of food is required by a 

 horse at any particular kind of work, it is necessary to 

 determine how much food is used up by the body when 

 the animal is doing no external work at all. Even at 

 rest work is being done m the body, and this work 

 must be provided for by adequate supplies of food and 

 air. The ordinary petrol motor affords a good illustra- 

 tion of this point. On disconnecting the gearing, the 

 forward or backward movement is stopped, and the con- 

 veyance pulled up, although the motor continues to work 

 with expenditure of energy, and petrol continues to 

 be used. Stop the supply of petrol, and the machine 

 stops altogether. In the horse at rest a considerable 

 amount of work is being done : the heart is beating to 

 drive round the blood ; the chest muscles are contract- 

 ing to pump air in and out ; the digestive apparatus is at 

 work manufacturing and pouring out the various juices 

 needed to dissolve the useful parts of the food, mixing 

 and moving on the ingested material from stomach to 

 small intestine, and from small intestine to large, finally 

 excreting the waste material ; the kidneys are filtering off 

 waste products separated from the useful material by the 

 liver ; and over and above all, controlling and co-ordinat- 



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